Exposure regulating device for photographic cameras



April 25, 1961 F. BIEDERMANN ETAL 2,981,168

EXPOSURE REGULATING DEVICE FOR PHOTOGRAPHIC CAMERAS Filed Aug. 2, 1957 INVENTORS Fr/karich B/EDERMANN Anion Z/NKL United States PatentO EXPOSURE REGULATLNG DEVICE FOR PHOTOGRAPHIC CAMERAS Friedrich Biedermann and Anton Zinkl, both of Unterhaching, near Munich, Germany, assignors to Agfa Aktiengesellschaft, Leverkusen-Bayerwerk, Germany, a corporation of Germany Filed Aug. 2, 1957, Ser. No. 675,894 Claims priority, application Germany Oct. 5, 1956 Claims. (Cl. 95-53) This invention relates to a pneumatic exposure regulating device for a photographic camera in which a reciprocating pump serves as a retarding device for the camera shutter, and more particularly relates to such device in which the reciprocating pump is a diaphragm type pump.

There are existing pneumatic exposure regulating devices in which a reciprocating air pump serves as a retarding means for the shutter. Some of these retarding devices include a perforated valve plate and an associated movable flow-obstructing member. Movement of this flow-obstructing member may be photoelectrically controlled to permit it to control the effect of the retarding device in accordance with the existing available illumination for photographic exposures. The diaphragm type of pump has been utilized in some of these retarding devices, but in the form in which it has been used it has been rather sluggish in operations.

In accordance with this invention, the surface of the cylinder head of a diaphragm type pump adjacent the diphragm is uniquely shaped or profiled, for example, in

an approximately cone-shaped form.

This form is constructed and arranged to correspond to the configuration which the diaphragm and element a which connects the diaphragm to the pump rod naturally assume in a critical operating position of the retarding device.

In accordance with a preferred embodiment of this invention, the cylinder head of the diaphragm pump is constructed and arranged as a specially profiled insert which is placed between the valve plate and the diaphragm. This profiled insert includes a central orifice which is connected with the orifices in the valve plate by means i 5 As is later explained in detail, this mvent1on provides the advantage that the movable components of the diaphragm pump have a relatively large working stroke while the volume of air between the diphragm and the cylinder head at the beginning of the stroke is reduced to a minimum. This makes it possible to precisely regulate the retarding effect upon the shutter substantially throughout the entire working stroke which provides a relatively great degree of control over the orifice area of the retarding device for regulating the shutter speed or exposure time.

Novel features and advantages of the present invention will become apparent to one skilled in the art from a reading of the following description in conjunction with the accompanying drawings wherein similar reference characters refer to similar parts and in which:

5 phragm 8.

Fig. 1 is a cross-sectional view in elevation of an embodiment of this invention;

Fig. 2 is a plan view of a portion of the embodiment shown in Fig. 1; and

Fig. 3 is a cross-sectional view in elevation of a portion of another embodiment of this invention.

In Fig. 1 is shown a portion 1 of the camera housing including a plate 2 for example, horizontally disposed a short distance below the top of the housing cover 3. A pneumatic retarding device for example, a diphragm type pump, is disposed within portion 1 and includes a cylinder 4 having a valve disc 6 perforated withorifices 5. A diaphragm 8 is mounted or secured between the walls of the cylinder 4 and a mounting ring 7. A connecting rod 9 is coupled with diphragm 8 substantially at its center by means of flanges 10 and 11. The other end of rod 9 is connected for example, by means of a connecting linkage to a movable element (not shown) of the shutter (not shown). This movable element is characterized in that the exposure time provided by the shutter is a function of the speed of movement of the movable element. This movable element is, for example, the main drive member of the shutter, and this pneumatic retarding device is, for example, generally similar to the device disclosed in Belgian Patent 516,387 granted on January 15, 1953. However, this present device includes features not therein disclosed which are described in detail in the following:

A flow-obstructing member 12 is disposed over and substantially parallel to valve plate 6. Flow-obstructing member 12, for example, is supported on the rotating shaft 13 connected for example, to the rotating coil of a galvanometer 14 which is part of a photoelectric exposure measuring device (also not shown). This shaft 13 rotates in accordance with the photocurrent flowing through the coil of galvanometer 14 to cause flow-obstructing member 12 to move in a path parallel to valve plate 6 and thereby cover a greater or smaller number of orifices 5 in valve plate 6. In this manner, the retarding action imposed upon the shutter by the diphragm pump is automatically adjusted in accordance with the photocurrent flowing through the galvanometer coil which results in automatic regulation of the shutter speed and exposure time in accordance with the ambient illumination.

In Fig. l is also shown a ring-shaped insert 15 disposed in the cylinder head between valve plate 6 and diaphragm .8. The surface 16 of insert 15 adjacent diphragm 8 is constructed and arranged in an approximate cone shape. This allows the diphragm 8 in the position shown in Fig. 1, which it assumes when the shutter is tensioned or cocked, to closely adhere to surface 16. On orifice or aperture 17 is centrally disposed, for example, within insert 15 to conduct a flow of air into the cylinder and to receive flange 11 which helps connect rod 9 to dia- When the shutter is tensioned or cooked, flange 11 is, therefore, received within orifice or aperture 17 without any extra space being necessitated between diaphragm 3 and surface 16. This permits diaphragm 8 to closely adhere to all adjacent portions of surface 16 of ring-shaped insert 15. A shallow recess 19 is provided in the upper portion of ring-shaped insert 15 adjacent orifices 5. A connecting channel is thereby formed between outer surface 18 of insert 15 and the adjacent inner surface of valve plate 6 through which air passes from orifices 5 to aperture 17 and subsequently into the cylinder.

This reduces the air volume or space between diaphragm 8 and valve plate 6 to a minimum when the shutter is in a tensioned position. This permits the braking or retarding effect of diphragm 8 to be developed a relatively short time after rod 9 begins to move. This provides a relatively great range of control over the effect of the retarding device upon the camera shutter.

The approximate conical shaping of surface 16 of the cylinder head of the diaphragm pump permits the diaphragm 8 to change its shape relative to the cylinder head from a concave curve at the beginning or top dead center position of the stroke to a convex curve at the end or bottom dead center position of the stroke which is shown in broken line. This provides the additional advantage of a relatively large working stroke of rod 9 without excessive twisting of diaphragm 8.

As shown in Fig. 3, valve plate 6 and'insert 15 of Fig. 1 can be replaced by -a unitary cylinder head element an. In this embodiment orifices are extended through cylinder head 2t) which permits them to be constructed and arranged in forms other than cylindrical, such as in tapered forms.

What is claimed is:

1. In combination with a photographic camera including a shutter, an exposure regulating device comprising a cylinder, a cylinder head, a flexible diaphragm mounted Within said cylinder, connecting means coupling said diaphragm to a movable element of said shutter, said movable element being characterized in that the exposure time provided by said shutter is a function of the speed of moveinent of said element to permit said diaphragm to retard said shutter, a perforated valve plate including orifices a minimum space between said diaphragm and said concave surface of said cylinder head at this condition.

2. An exposure regulating device as set forth in claim 1 wherein said concave surface of said cylinder head is formed upon a ring-shaped insert which is disposed between said valve plate and said diaphragm, and the edge of said diaphragm being secured between said insert and said cylinder.

3. An exposure regulating device as set forth in claim 1 wherein said cylinder head and said valve plate are formed in a unitary structure, and said orifices extend through said cylinder head into the space adjacent said diaphragm.

4. In combination with a photographic camera including a shutter, an exposure regulating device comprising a cylinder, a cylinder head, a flexible diaphragm mounted within said cylinder, connecting means extending on both sides of said diaphragm coupling said diaphragm to a movable element of said shutter, said movable element being characterized in that the exposure time provided by said shutter is a function of the speed of movement of said element to permit said diaphragm to retard said shutter, a perforated valve plate including orifices, connected to said cylinder head, the surface of the head of said cylinder adjacent said diaphragm and said diaphragm being constructed and arranged in a form which provides a minimum space betweensaid diaphragm and said surface at the extremity of travel of said diaphragm corresponding to the tensioned position of said shutter, and a recess substantially centrally disposed in said cylinder head for receiving said connecting means to permit said diaphragm to closely contact substantially all of the adjacent surface of said cylinder head when said movable element of said shutter is in said tensioned position.

5. In combination with a photographic camera including a shutter, an exposure regulating device comprising a cylinder, a cylinder head, a flexible diaphragm mounted within said cylinder, connecting means extending on both sides of said diaphragm coupling said diaphragm to a movable element of said shutter, said movable element being characterized in that the exposure time provided by said shutter is a function of the speed of movement of said element to permit said diaphragm to retard said shutter, a perforated valve plate including orifices connected to said cylinder head, the surface of the head of said cylinder adjacent said diaphragm and said diaphragm being constructed and arranged in a profiled shape which provides a minimum space between said diaphragm and said surface at the extremity of travel of said diaphragm corresponding to the tensioned position of said shutter, said profiled shape of said cylinder head being formed upon a ring-shaped insert which is disposed between said valve plate and said diaphragm, said insert including a central aperture for receiving said connecting means, and a shallow recess being provided upon the surface of said insertadjacent said valve plate and connecting said central aperture with said orifices to provide a channel from said orifices through said ring-shaped insert into said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 2,800,844 Durst et al. July 30, 1957 FOREIGN PATENTS 489,348 Italy Ian. 19, 1954 

